Construction Plan for 5000 Ton Low Temperature Storage Center Cold Storage Project in Logistics Park

Construction Plan for 5000 ton Low temperature Storage Center Cold Storage Project in Logistics Park

Tiwen: In response to the continuous development and construction of logistics cold storage, this solution starts from bare ground and adopts the situation that best meets the actual work needs of customers. Combining theory with practice and years of experience, we provide a cold storage solution with a stock of 5000 tons.

catalogue

1. Location selection

2. Estimation of storage tonnage and construction area

3. Architectural Structure Description

4. Cold storage layout division/functional zoning

5. Cold storage insulation materials

6. Cold storage refrigeration system scheme

7. Cold storage shelf tray scheme

8. Engineering energy consumption index

9. Construction period and estimate

10. Conclusion

1、 Site selection

Logistics warehousing and cold storage facilities are generally built in locations with cheap land prices and relatively convenient transportation according to the development of the enterprise itself. The area around the cold storage facility should avoid heavy pollution sources, and the floor should be flat, hard, and dry. The ground surface is generally made of concrete, and the warehouse door should be facing away from the wind direction. The door opening direction can be towards the east and away from the pollution source. The floor elevation should be higher than the surrounding ground to prevent water from entering the warehouse.

Consider factors such as convenient transportation and market connectivity. Cold storage should be built in a cool and shady place without frequent hot air. There should be good drainage conditions around the cold storage, low groundwater level, insulation layer under the cold storage, and good ventilation and dryness are important for the cold storage. In addition, before the construction of the cold storage, the corresponding three-phase power should be installed according to the power of the freezer.

2、 Calculation of tonnage and area for construction

Generally, high-temperature warehouses mainly store fruits and vegetables, which are packaged in cardboard boxes. The density of the goods can be around 280-330kg/cubic meter, and the utilization rate of the warehouse can be selected from 0.5-0.6. The warehouse is equipped with shelves, transportation channels, and ventilation ducts for top refrigeration equipment. The inventory can be stored for about 5 cubic meters per ton of goods. The inventory situation of each warehouse may not be similar. Low temperature cold storage is generally used to store poultry and seafood goods. For example, the density of such goods, such as white meat, is about 420kg/cubic meter, and the storage volume coefficient is 0.5-0.6. Therefore, low-temperature cold storage can choose about 4 cubic meters to store one ton of goods. The above inventory levels are for reference only, and the actual inventory stacking may vary depending on different goods and packaging stacking.

Regarding the explanation of the volume coefficient, some goods are stacked to the brim, while others do not require shelves and are stacked in multiple layers. Additionally, this stacking method involves stacking goods on top of each other, but it takes a longer time for the center temperature and pressure of the goods to reach the desired temperature. The operating time of its refrigeration equipment will be longer. Relatively speaking, it will increase the cost of electricity. Reasonable use of shelves and stacking of goods can save energy and reduce operating electricity costs. It is recommended to use reasonable shelves and leave good air ducts for large cold storage facilities. The placement of goods and the air ducts of the air coolers should be in line with the airflow flow. Easy to achieve average storage temperature.

For example, with a storage capacity of 10000 cubic meters, after the construction of a high-temperature warehouse, it can store about 1200 tons of fruits and vegetables at a ratio of 10000 * 0.6/5. A high-temperature low-temperature warehouse can store approximately 1500 tons of frozen poultry meat.

The above is just a theory. In fact, some of the small cold storage facilities we have worked in have very full piles of goods from ground to top during peak seasons, and very few goods during off-season. The tonnage of large logistics warehouses shall be planned based on actual operations.

3、 Cold storage structure and main description

At present, most of the warehouse construction is mainly based on single-layer steel structures, with steel structures on the outside, assembled warehouse bodies, unloading platforms, ammonia/fluorine refrigeration systems, control systems, pipeline connections, etc., forming a cold storage project. Then, a basic cold storage project is composed of a refrigeration system, piping system, and control system. After the cold storage is built, shelves, transport stacker trucks, RFID barcode tag management system, monitoring system, and other equipment will be added to the interior of the warehouse. The unloading platform of the low-temperature cold storage should be designated as a low-temperature area, and a low-temperature platform with a temperature range of 0-10 degrees can be built. Multi story cold storage is made of brick and steel structures, with materials including assembled storage panels and on-site foam spraying insulation. The assembled warehouse board mainly uses polyurethane rigid foam as the thermal insulation material. Since the 1970s, it has been used in the field of building thermal insulation in Europe, America and other developed countries. After more than 30 years of popularization and application, polyurethane has become the most important material for refrigeration and thermal insulation. Double sided color steel plates or stainless steel plates are used, with eccentric hooks embedded in the plate body. The insulation characteristics of using this type of storage plate are fast construction period, good insulation performance, and strong economic performance. It is currently the main insulation method in cold storage projects. When choosing polyurethane insulation board, attention should be paid to density, steel plate thickness, flame retardancy, and water absorption rate.

4、 Selection of refrigeration host system

At present, the main refrigerants used for building cold storage in the market are ammonia and fluorine refrigeration systems, and there are also many that use CO2 refrigeration. However, relatively speaking, fluorine systems are more commonly used in small and medium-sized engineering projects. For systems with a scale of over 10000 tons, ammonia and CO2 systems are more suitable. Freon R507A is a green and environmentally friendly refrigerant that does not damage the ozone layer, is non-toxic, and does not explode. The comparison between ammonia refrigeration system and green and environmentally friendly fluorine refrigeration system can be made in terms of economy, energy saving, safety, automation level, system complexity, later scalability, investment and operating costs, construction difficulty and duration, and use and maintenance. Detailed comparative analysis will be explained separately. Due to limited space, we will not provide a detailed discussion at this time. The following project adopts a fluorine system.

Compare from six aspects: system operating costs, labor costs, daily maintenance costs, major overhaul costs, and annual replenishment of refrigerant and refrigeration oil

Fluorine based refrigeration systems (referring to traditional Freon refrigerants and alternative green and environmentally friendly refrigerants) can be compared with ammonia based refrigeration systems in terms of energy efficiency and system operation safety. The specific comparison is as follows.

1. Energy efficiency

a) The full liquid system of the ammonia machine provides a single, stable evaporation pressure, but its ability to adjust and adapt to temperature changes is poor. For situations where the temperature is often fluctuating, such as frequent storage and heating, the heat transfer temperature difference will be large under variable temperature conditions, which means a decrease in efficiency. Usually, increasing the heat transfer temperature difference by 1 degree Celsius will cause an increase of nearly 3% in energy consumption; For the fluorine system that directly supplies liquid, due to its good regulating function through the expansion valve, its efficiency under the same conditions is higher than that of the full liquid system of the ammonia machine. The increase in external heat transfer temperature difference also means an increase in dry consumption, which can lead to a decrease in product quality and loss of product weight.

b) For large single machine systems, the vast majority of the actual operation time is under partial load. For compressors that can be energy regulated, especially screw compressors, their energy efficiency ratio at partial load is lower than that at full load. Especially when the load drops below 70%, the energy efficiency ratio decreases significantly. Therefore, the actual operating cost of single machine systems will be much higher than the evaluation value calculated using full load energy efficiency ratio; For parallel systems and SRS (Distributed Refrigeration System), energy regulation is achieved by controlling the on/off of the compressor, which ensures that each head of the unit maintains its highest energy efficiency ratio during partial load operation, greatly reducing the actual operating costs of the system.

2. Security

a) The green and environmentally friendly refrigerant R507A is the safe working fluid used in this project, which is colorless, odorless, non combustible, and non explosive; Ammonia is colorless, toxic (second level toxicity), and contains a strong irritant odor. It has a strong irritant and poisoning risk to the eyes, nose, throat, lungs, and skin. When the concentration in the air exceeds 15%, there is an immediate risk of fire and explosion. Based on the above drawbacks, it will be prohibited in densely populated public places and workplaces. The ammonia refrigeration system is therefore subject to approval management and operational supervision by the national safety production management department.

b) In addition, the parallel technology of the fluorine system has been developed very well, and the parallel system will not affect the normal operation of the entire system due to individual compressor failures or maintenance needs during operation. Moreover, compared to a single machine system that generates the same amount of cooling, the average operating time of each compressor in a parallel unit is much shorter than that of a single machine cooling system, resulting in a longer service life of the compressor.

3. Degree of automation

The SRS control system controls the on/off of the compressor in the unit based on the thermal load, thereby achieving control over the storage temperature. We can set the upper and lower limits of the storage temperature on the centralized control screen, and this temperature difference can be set very small, which is very beneficial for the quality of food stored in the warehouse during storage. The domestic ammonia system generally controls the storage temperature manually, and determines the number of compressors to start or stop based on personnel's observation of the storage temperature. Because all operations are manually carried out by personnel, it depends on the technical level and sense of responsibility of the operators. So this job requires a very high level of personnel quality. According to a survey of industry operators, it generally takes 5-10 years to train a qualified ammonia machine operator. Moreover, even qualified operators have many uncertain factors in the operation of machines and systems, such as their sense of responsibility and excessive fatigue, which can affect the normal use and even safety of the equipment. The ammonia system requires someone to be on duty 24 hours a day and make adjustments.

4. Comparison of System Complexity

The fluorine system has a compact structure with few accessories, and most of the units can be completed in the factory. The quality of the system is fully guaranteed; Due to the inability to find suitable lubricating oil that is miscible with ammonia, the ammonia system requires a large number of accessories to ensure oil return and reduce system temperature, resulting in a complex system that requires extensive on-site installation work. The quality of the system largely depends on the quality of the installation team. The compact structure and small footprint of the fluorine system also make it possible to arrange units in corridors or on rooftops.

5. Scalability

After the design and installation of the ammonia system is completed, it is generally not realistic to expand it due to business development needs. The flexibility of the fluorine system is much stronger.

The use of fluorine system is more flexible, and it can achieve centralized cooling or separate cooling according to current needs. When expanding, it is small and convenient, and even expansion units can be arranged in channels or roofs without renovating the computer room.

6. Investment amount and operating expenses

If the same level of automation is achieved and the same level of accessories are used, the cost of the fluorine system will be lower than that of the ammonia system.

The ammonia system occupies a large area, and the investment in civil engineering is far less than that of the small-scale units of the fluorine system. The saved space can be used for production. In addition, due to the compact structure and small footprint of the fluorine system, it is particularly suitable for renovation and additional investment.

Considering efficiency reasons, the operating cost of the fluorine system is lower than that of the ammonia system.

Considering the degree of automation, the ammonia system requires 24-hour duty (number of machine heads+1/single shift), while the fluorine machine only requires regular or irregular inspections by maintenance personnel. Considering maintenance costs, open type shaft seals are vulnerable parts that require regular inspection and replacement, while semi closed machine heads do not have this concern.

7. Simple construction and controllable schedule

The construction of ammonia system is complex. As ammonia is a hazardous working fluid, each weld seam of the ammonia system must undergo inspection by the technical supervision bureau and pass the inspection before it can be used. The construction period is long and cannot be well controlled; Most of the fluorine system units are assembled in factories, with reliable on-site construction, high efficiency, short construction period, and controllability. For users, completing them one day earlier means producing and making profits one day earlier.

5、 Customer requirements for this project

The customer mainly engages in logistics and distribution. We have newly built a 20000 cubic meter cold storage with a temperature range of -18 to -25 ℃, which can store various low-temperature poultry meat, cold drinks, and other goods. Low temperature enclosed platforms are installed at both ends.

Schematic distribution diagram of cold storage floor plan

6、 Project Overview

The size of the cold storage in this project is 75 × 35 × 7m, divided into 6 storage rooms, equipped with 6 unloading platforms and 6 electric sliding doors. The cold storage adopts a steel structure and assembled storage body, and the refrigeration equipment adopts a Bizelle screw parallel refrigeration unit. The condenser adopts an evaporative condenser

All evaporators in the warehouse are made of aluminum pipes The defrosting method adopts hot fluorine defrosting The cold storage insulation board adopts 150mm thick polyurethane double-sided color steel plate.

Outline drawing of building structure: The building structure adopts steel frame method.

Raise the foundation by 1.2 meters and embed 250mm cement ventilation pipes. Carry out waterproof, moisture-proof, and insulation layer treatment.

7、 System control mode

Adopting Siemens PLC centralized management automation control and touch screen settings, it can flexibly manage cold storage equipment. By using computer software management, multiple libraries can be centrally managed, with functions such as over temperature sound and light alarm, over temperature SMS reminder alarm, etc.

8、 Project duration

The civil construction is completed, and the cold storage project begins construction, which takes 70 days.

Project location: Shanghai

9、 Main equipment list:

Composed of 1 refrigeration compressor unit, 1 evaporative condenser, 1 barrel pump unit, 1 horizontal liquid storage tank, and 1 intelligent temperature monitoring system.

10、 Closed low-temperature platform

The cold storage of this project adopts a closed unloading platform, which effectively prevents the occurrence of cargo breakage. Using a closed low-temperature platform can maximize the quality of frozen products during circulation, significantly reduce the heat load from the outside due to temperature differences, and greatly reduce the amount of moisture entering the low-temperature space.

11、 Description of refrigeration and accessory equipment

Refrigerant: R507 is used, which has the characteristics of colorless, odorless, and non-toxic.

Refrigeration host: Adopting a Bizelle low-temperature screw three parallel unit, it has the characteristics of high efficiency, long service life, low vibration, and low noise. Equipped with an economizer, increase the compressor's suction capacity and liquid subcooling to improve cooling capacity. The compressor is equipped with exhaust temperature protection, oil pressure protection, motor overload protection, etc.

Internal evaporator: Installed on site with aluminum pipes, it has the characteristics of uniform cooling, good insulation effect, and small temperature fluctuations in the warehouse. At the same time, it has better quality for storing goods.

Refrigeration accessories: Danfoss series products are used.

Evaporative condenser: It uses the spray water outside the coil to partially evaporate and absorb the evaporative condenser inside the coil

The heat of the high-temperature gaseous refrigerant gradually cools the refrigerant inside the tube from a gaseous state to a liquid state. Compared with water and air cooling, it can save 17% electricity. And the operating cost is low.

Floor insulation

Prepare the foundation, embed 250mm cement pipes, compact 400mm of backfill soil on top, pour a 5cm layer of concrete, then apply a waterproof layer, 3mm SBS modified asphalt waterproof treatment, lay plastic film, then lay 150mm thick XPS extruded board on top, lay a thin film layer on top, and finally pour 150mm concrete and 5mm thick diamond sand surface layer. After this treatment, it can not only provide insulation and moisture resistance, but also ensure the load-bearing capacity of the floor. XPS insulation board has good insulation performance, chemical stability and physical structure with good durability, low thermal conductivity, strong water resistance, good compressive strength and flame retardancy. At the same time, this product has no harmful substance volatilization and has good corrosion resistance.

Defrosting method

This time, the air cooler adopts the method of hot fluorinating frost, which can save a lot of costs compared to using electric heating defrosting. The principle of hot fluorine frost is to introduce the high-temperature and high-pressure refrigerant gas discharged from the compressor into the evaporator coil to melt the frost and ice layers on the coil. If electric heating defrosting method is used, the cost is: 8 DD-200 air coolers, with a defrosting power of 22.8KW per fan, totaling 183KW for 8 units. Defrosting is done every 4 hours for 30 minutes each time, and the daily electricity consumption is 549KW x 183KW x 0.5 hours=549KW. This defrosting method can save 549KW x 30 days x 12 months=200000 yuan in electricity bills per year in terms of energy saving, saving at least 200000 yuan in electricity bills per year. The initial investment cost of hot fluoride cream is very small, and compared with traditional electric heating cream, this project highlights the energy-saving advantages.

Computer room piping

Conclusion: In response to the continuous development and construction of logistics cold storage, we adopt the most suitable situation for customers' actual work needs, combine theory with practice and years of experience, and provide customers with reasonable refrigeration solutions. Save investment for customers and generate good economic benefits. The project is operational and can save customers 200000 yuan in electricity bills annually. The performance of its aluminum exhaust pipe and the hot fluorine frost technology have improved the refrigeration efficiency and cost saving principle in this project, meeting both the customer's needs and the expected budget requirements.